The present invention relates to aircraft control systems. In particular, the present invention to relates to a nacelle control system in a tiltrotor aircraft.
Flying a tiltrotor aircraft is a complicated and demanding task. The pilot must be aware of many things going on at once. In particular, the pilot must be aware of the ever-changing operating conditions of the aircraft and all of its systems. To do this, the pilot must scan multiple control panels and gauges to determine the operating condition of the many systems of the aircraft. Failure by the pilot to carefully monitor these systems can lead to serious problems. Because flying a tiltrotor aircraft is such a demanding task, designers are constantly considering ways to reduce pilot workload.
Although there have been great strides in tiltrotor aircraft technology, many shortcomings remain. Conventional tiltrotor aircraft have the following shortcomings: (1) it is possible for an inattentive pilot to operate the tiltrotor aircraft outside its nacelle angle-speed flight envelope; (2) there is no automated nacelle control, or means for switching between manual and automated control modes; (3) there are no preprogrammed nacelle angle indicators in the flight control computers; (4) fault detection for electrical failures and back-up switching for mechanical faults are inadequate; and (5) there is no automatic engagement of a maintenance mode.
In addition, as tiltrotor aircraft become more widely available for civil use, it is likely that certain operational guidelines and regulations will be implemented. Such operational guidelines and regulations may include certain standards and procedures, such as terminal area procedures for tiltrotor aircraft. No efforts have been made to mechanize the control of tiltrotor nacelles in anticipation of such standards and procedures be implemented.
There is a need for a multi-mode tiltrotor nacelle control system with integrated envelope protection.
Therefore, it is an object of the present invention to provide a multi-mode tiltrotor nacelle control system with integrated envelope protection.
The above objects are achieved by providing a multi-mode tiltrotor nacelle control system with integrated envelope protection having three modes of operation: an automatic mode, a semi-automatic mode, and a maintenance mode. The nacelle control system of the present invention includes a power lever thumbwheel with which the pilot can switch between the various modes of operation. There is triple redundancy in the nacelle control system in that switches are disposed on the pilot""s power lever, the co-pilot""s power lever, and the flight control panel.
The present invention reduces pilot workload associated with the fourth primary control for tiltrotor aircraft, i.e. nacelle rotation, by providing semi-automatic nacelle control and automatic mode switching. With the present invention, flight safety is improved by protecting the pilot from operating the aircraft outside its nacelle angle-speed flight envelope. In addition, the present invention improves pilot situational awareness by providing pre-programmed nacelle angle detents and cockpit indications consistent with the nacelle rate inhibit logic in the FCC""s. Also, the present invention improves the reliability of nacelle conversion systems by utilizing redundant, simple switches, providing in-line fault detection for electrical failures, and providing back-up switches to protect against mechanical faults. Furthermore, the present invention improves the safety of maintenance operation by automatically engaging a maintenance mode that utilizes slower nacelle rotation rates.
The present invention provides the following advantages: (1) high reliability for a tiltrotor nacelle conversion system; (2) mitigation of safety hazards associated with tiltrotor flight envelope exceedance; (3) reduction in flight crew workload to permit single pilot tiltrotor operations; (4) easy pilot access to maximum conversion rate for a power-off, e.g. dual engine failure, re-conversion maneuver; and (5) a mechanized means for complying with anticipated standards and procedures for the control of tiltrotor aircraft.
The above objects and advantages, as well as others, will be evident from the following detailed description of the present invention.